Transplantation of osteoblast-like cells to the distracted callus in the rabbit mandible.

BACKGROUND

The purpose of this study was to investigate whether injections of marrow-derived mesenchymal progenitor cells could be used to facilitate new bone formation during distraction osteogenesis.

METHODS

Fifteen New Zealand rabbits underwent bilateral osteotomy. After a 1-week latency period, bone distraction was activated at a rate of 2.0 mm/day for 5 days. The marrow-derived mesenchymal progenitor cells derived from the ilium marrow were cultured to a population of 10 in 0.5 ml and then unilaterally transplanted to the gap of distracted callus immediately after distraction had been terminated. Rabbits were killed at 2, 4, and 6 weeks after completion of bone lengthening. The distracted areas were harvested and evaluated by histologic, histomorphometric, radiographic, and scanning electron microscopic analysis. Bone mineral density in the lengthened callus was evaluated using dual-energy x-ray absorptiometry.

RESULTS

Radiographic evaluation indicated a significant increase in bony union of the distraction regenerate in the experimental side compared with the control side. Corresponding to the radiographic findings, the histologic examination showed an earlier and more intensive bone formation in the experimental side after 2, 4, and 6 weeks compared with the control side. Larger chondroid islands were found evident in distracted bone of the control side than in the experimental side.

CONCLUSIONS

The results show that transplantation of osteoblast-like cells promotes maturity of the distracted callus, as observed on the second and fourth weeks after lengthening. The method appears promising as a means of shortening the consolidation period of osteodistraction and decreasing complications during bone lengthening.